The present invention relates generally to the use of lubricants in connection with magnetic recording media and, in particular, to the use of lubricants for reducing frictional coefficients of thin-film recording media.
Thin-film magnetic discs or media are used as data storage media for digital computers. The discs typically are formed by successively sputtering various layers onto a rigid disc substrate. The sputtered layers can include an underlayer, a magnetic layer, and a carbon overcoat which protects the magnetic layer from corrosion and oxidation and reduces frictional forces between the disc and a read/write head.
The surface of the disc is often lubricated with a thin film of a lubricant to reduce friction between the head and the disc, particularly during start and stop cycles. The lubricity of a disc-head interface generally is measured in terms of dynamic and/or static coefficients of friction or stiction values. Dynamic stiction values can be measured using a standard drag test in which the drag produced by contact of a read/write head with a disc is determined at a constant spin rate, for example, 1 rotation per minute (rpm). Static stiction values can be measured using a standard contact start-stop (CSS) test in which the peak level of friction is measured as the disc starts rotating from zero to a selected revolution rate, for example, 5,000 rpm. After the peak friction is measured, the disc is brought to rest, and the start-stop process is repeated for a selected number of start-stop cycles.
For good long-term disc and drive performance, the disc-head interface should retain a relatively low stiction value after many start-stop cycles or contacts between the disc and a read/write head. For example, a drive manufacturer may require that the disc-head interface have a stiction value no greater than 1.5 or 3 after 15,000 start-stop cycles. A disc that meets such requirements can tolerate at least 15,000 start-stop cycles without exhibiting high friction characteristics that would interfere with the read/write operations. Improvements in the manufacture of discs are desirable to reduce the wear and improve the long-term performance of the magnetic discs.